There are many conventional ways to scan a laser beam over a solid angle. However, each of these conventional scanning techniques is associated with one or more problems.
For example, dual galvanometers are used in many scanning operations, but have a large dual axis. Dual acousto-optic scanners, dual electro-optic scanners, and dual electro-optic scanners are each associated with a small scan angle (6 optical degrees or less). Dual electro-optic scanners are also physically very large. Dual resonant scanners are associated with a difficult random axis in solid angles unless there is a mechanism to change the resonance of each axis. Dual “stress optical beam” scanners have a small scan angle (15.5 optical degrees using GaAs). Dual gradient liquid crystal scanners also exhibit a small scan angle (0.57 optical degrees). Dual MEMS electro-static scanners have a small scan angle (<30 degree optical scan angle) and a small aperture (1-2 mm). Risley prism scanning assemblies exhibit beam distortion at the edge of scan and an anomaly at zero degree scan angle. Also, for multiple wavelengths, each Risley prism scans at a different angle unless a reflective Risley is used which is quite large. Spinning hologon, dual rotating polygon (transmissive or reflective), trepanning (move the lens), and dual rotating gratings are all scanning techniques associated with a large size. Dual phased arrays exhibit low power density.
A combination of any of these conventional single axis scanning techniques can also be used to make a dual axis scanning system. However, such a combination merely provides a combination of the associated problems.
What is needed, therefore, are compact scanning techniques that can scan a large degree optical solid angle.